如何将一个数组复制到目标c中不在同一类中的另一个数组？

//FirstClass .h file
#import @\"SecondClass.h\"
@interface FirstClass : NSObject {
    NSArray         *firstArray; 
    SecondClass     *sec; 
}
@property(nonatomic, retain) NSArray        *firstArray; 
@property(nonatomic, retain) SecondClass    *sec; 
@end

//Add this to FistClass .m file
@synthesize firstArray, sec; 

-(id)init{
    if(self == [super init]){
        sec = [[SecondClass alloc] init];
        firstArray = [[NSArray alloc] initWithArray:sec.secondArray];
    }
    return self; 
}

-(void)dealloc{
    [firstArray release];
    [super dealloc];
}

//SecondClass .h file
@interface SecondClass : NSObject {
    NSMutableArray          *secondArray;  
}
@property(nonatomic, retain) NSMutableArray     *secondArray; 
@end

//Add this to SecondClass .m file
@synthesize secondArray; 

-(id)init{
    if(self == [super init]){
        secondArray = [[NSMutableArray alloc] initWithObjects:@\"Obj1\", @\"Obj2\", @\"Obj3\", nil];//etc... 
        //Maybe add some more objects (this could be in another method?)
        [secondArray addObject:@\"AnotherObj\"];

    }
    return self; 
}

-(void)dealloc{
    [secondArray release];
    [super dealloc];
}